/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.db.metadata.schemaregion;

import org.apache.iotdb.commons.consensus.SchemaRegionId;
import org.apache.iotdb.commons.path.PartialPath;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.LinkedList;
import java.util.List;

public class RSchemaRegionLoader {
    private static final Logger LOGGER = LoggerFactory.getLogger(RSchemaRegionLoader.class);
    private static URLClassLoader urlClassLoader = null;
    private static final String RSCHEMA_REGION_CLASS_NAME =
            "org.apache.iotdb.db.metadata.schemaregion.rocksdb.RSchemaRegion";
    private static final String RSCHEMA_CONF_LOADER_CLASS_NAME =
            "org.apache.iotdb.db.metadata.schemaregion.rocksdb.RSchemaConfLoader";
    private static final String LIB_PATH =
            ".." + File.separator + "lib" + File.separator + "rschema-region" + File.separator;

    public RSchemaRegionLoader() {
    }

    /**
     * Load the jar files for RSchemaRegion and create an instance of it. The jar files should be
     * located in "../lib/rschema-region". If jar files cannot be found, the function will return
     * null.
     *
     * @param storageGroup
     * @param schemaRegionId
     * @return
     */
    public ISchemaRegion loadRSchemaRegion(PartialPath storageGroup, SchemaRegionId schemaRegionId) {
        ISchemaRegion region = null;
        LOGGER.info("Creating instance for schema-engine-rocksdb");
        try {
            loadRSchemaRegionJar();
            Class<?> classForRSchemaRegion = urlClassLoader.loadClass(RSCHEMA_REGION_CLASS_NAME);
            Class<?> classForRSchemaConfLoader = urlClassLoader.loadClass(RSCHEMA_CONF_LOADER_CLASS_NAME);
            Constructor<?> constructor =
                    classForRSchemaRegion.getConstructor(
                            PartialPath.class, SchemaRegionId.class, classForRSchemaConfLoader);
            Object rSchemaLoader = classForRSchemaConfLoader.getConstructor().newInstance();
            region = (ISchemaRegion) constructor.newInstance(storageGroup, schemaRegionId, rSchemaLoader);
        } catch (ClassNotFoundException
                | NoSuchMethodException
                | InvocationTargetException
                | InstantiationException
                | IllegalAccessException
                | MalformedURLException
                | RuntimeException e) {
            LOGGER.error("Cannot initialize RSchemaRegion", e);
            return null;
        }
        return region;
    }

    /**
     * Load the jar files for rocksdb and RSchemaRegion. The jar files should be located in directory
     * "../lib/rschema-region". If the jar files have been loaded, it will do nothing.
     */
    private void loadRSchemaRegionJar() throws MalformedURLException {
        LOGGER.info("Loading jar for schema-engine-rocksdb");
        if (urlClassLoader == null) {
            File[] jars = new File(LIB_PATH).listFiles();
            if (jars == null) {
                throw new RuntimeException(
                        String.format("Cannot get jars from %s", new File(LIB_PATH).getAbsolutePath()));
            }
            List<URL> dependentJars = new LinkedList<>();
            for (File jar : jars) {
                if (jar.getName().endsWith(".jar")) {
                    dependentJars.add(new URL("file:" + jar.getAbsolutePath()));
                }
            }
            urlClassLoader = new URLClassLoader(dependentJars.toArray(new URL[]{}));
        }
    }
}
